VXI VT1422A - Manual (Page 527)

Acquisition Acquisition
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Algorithmic Closed Loop Controller and
Remote Channel Multifunction
VT1415A/1422A
Timing Signals
Timing: Scan-to-scan timing and
sample-to-sample
timing can be set
independently.
Scan triggers: Can be derived from a software
command or a TTL level from
other VXI modules, internal timer,
or external hardware.
Typical latency 17.5 µs.
Synchronization: Multiple VT1415A/VT1422A
modules can be synchronized
at the same rate using the TTL
trigger output from one
VT1415A/VT1422A to trigger
the others.
Alternate Multiple VT1415A/VT1422A
synchronization: modules can be synchronized at
different integer-related rates
using the ALG:SCAN:RATIO
command and the TTL trigger
output from one VT1415A/
VT1422A module to trigger
the others.
Scan Triggers
Internal: 100 µs to 6.5536 s
Resolution: 100 µs
Trigger count: 1 to 65535 or infinite
Sample Timer VT1415A: 10 µs to 32768 ms
Range: VT1422A: 40 µs to 32768 ms
Resolution: 0.5 µs
Measurement Specifications
The following specifications include the SCP and scanning
A/D performance together as a unit. Accuracy is stated for
a single sample. Averaging multiple samples will improve
accuracy by reducing noise of the signal. The basic VT1415A
scanning A/D has a full-scale range of ±16 V and five auto-
ranging gains of x1, x4, x16, x64, and x256. An SCP must be
used with each eight channel input block to provide input
protection and signal conditioning.
Note: For field wiring, the use of shielded twisted pair
wiring is highly recommended.
Measurement resolution: 16 bits (including sign)
Maximum reading rate: VT1415A: Up to 56 kSa/s
dependent upon configuration
VT1422A: Up to 25 kSa/s
dependent upon configuration
Memory: 64 kSamples
Maximum input voltage: Normal mode plus
common mode
Operating: ±16 V peak
Damage level: ±42 V peak
Maximum common mode voltage:
Operating: ±16 V peak
Damage level: ±42 V peak
SCP input impedance: 100 MΩ differential
Maximum tare cal offset: 62.5 mV range ±75% of full
scale, other ranges ±25%
of full-scale
Jitter:
Phase jitter scan-to-scan: 80 ps rms
Phase jitter card-to-card: 41 ns peak 12 ns rms
Measurement Accuracy
Typically ±0.01% of input level; varies with the SCP used.
Specifications are 90 days, 23 °C ± 1 °C, with *CAL done after
a 1hr warm-up and CAL:ZERO done within 5 minutes. Note:
Beyond the 5min. limitation and CAL:ZERO not done, apply the
following drift error: Drift = 10 µV/°C ÷ SCP gain, per °C change
from CAL:ZERO temperature.
Accuracy Data
Measurement accuracy is dependent upon the SCP module used.
Refer to the accuracy tables and graphs for the individual SCP to
determine the overall measurement accuracy.
Many definitions of accuracy are possible. Here we use single-
shot with 3 sigma noise. To calculate accuracy assuming
temperature is held constant within ±1 °C of the temperature at
calibration, the following formula applies:
Single Shot 3σ = ±(√((GainError)2 + (OffsetError)2+ (3σ noise)2))
Correcting for Temperature